Laserfiche WebLink
Page 11 of 23 <br />Appendix l <br />Chemical Control of Russian Knapweed <br />In most circumstances, an herbicide alone will not effectively manage Russian knapweed. However, there <br />may be situations where desirable plants within a Russian knapweed infestation may compete effectively <br />with the weed if it is stressed with a single weed management technique. When integrating chemical and <br />cultural control, avoid using herbicide rates that injure grasses because effective competition will be <br />reduced. <br />Russian knapweed is controlled with 'Tordon 22K (picloranr) at 1 to 2 quarts/A. Tordon may be broadcast <br />sprayed up to 1 quart/A or spot sprayed at rates up to 2 quarts/A. Tordon plus 2,4-D (1 to 1.5 pints + 1 <br />quartlA) also will control Russian knapweed. If low rates of Tordon or Tordon plus 2,4-D are used, <br />application for two consecutive years may be necessary to achieve adequate control. Apply Tordon any <br />time the weed is actively growing. <br />For Telar (chlorsulfiuon), a noncrop herbicide that controls Russian knapweed, application timing is <br />critical. APPIY (1 orurcelA) when Russian knapweed is in the bloom to postbloom stage. Earlier <br />applications do not control the weed effectively. Fall is a good time to apply Telar, but it may injure smooth <br />brome or other brome species. Always add a good agricultural surfactant at 0.25 to 0.5 percent v/v to the <br />spray solution. Escort (metsulfuron) is labeled for pasture and rangeland use. Apply it at 0.75 to 1 ounce/A <br />with a good agricultural surfactant. Optimum timing for Escort is similar to Telar. <br />Mechanical Control of Russian Knapweed <br />Russian knapweed tends to form monocultures and usually eliminates other plants. Therefore, sowing <br />desirable plant species is necessary after the weed is controlled. Smooth brome will compete with Russian <br />knapweed. Research shows that streambank wheatgrass, thickspike wheatgrass, crested wheatgrass and <br />• Russian wildrye established after Russian knapweed was suppressed widr herbicides. Sod-forming <br />perennial grasses, like streambank or thickspike wheatgrasses, help prevent reinvasion better than bunch <br />grasses like crested wheatgrass. <br />If the Russian knapweed stand is not too old and grasses are still present, stimulating grass growth by <br />irrigation (where possible) should increase grass competition with knapweed and keep the weed under <br />continual stress. <br />Spotted knapweed <br /> <br />